Electrical musical instrument



Oct. 21-, 1947. J 'M. HANERT 2,429,226

' ELECTBICAL MUSICAL INSTRUMENT Filed Sept. 14, 1942 s sheets-sheet 1llallllltrvlvlllt'tull 5 Sheets-Sheet 2 J M. HANERT Oct. 21, 1947.

ELECTRICAL MUSICAL INSTRUMENT Filed Sept. 14, 1942 Oct. 21, 1947.,

J. (M. HANERT ELEQTRIOA L MUSICAL INSTRUMENT Filed Sept. 14, 1942 sSheets-Shet a Patented Oct. 21, 1947 ELECTRICAL MUSICAL INSTRUMENT JohnM. HanerhWilmette, 111., assignor to Hammond Instrument Company,Chicagoylll' acorporation of Delaware Application September 14, 1942',Serial No, 458,305

My invention relates generally to electrical musical instrumentsand-more particularly to improved duplex melody instruments upon whichtwo notes may be played simultaneously.

The invention is of peculiar utility when used as a substitute for, oras asupplement to, the bass or pedal clavier section of a pipe organ, orany-other type of organ. The pipes for the bass section of a pipe organare the largest and most expensive in the organ and, as a result, eventhe largest pipe organs are considerably limitedas to possible tonalvariation in their bass sections.

It is therefore an object of the invention to provide an improved meansfor producing the bass tones of. an organ.

A further object is to provide an improved frequency generating systemfor electrical musical instruments, utilizing the principle of-frequencydivision.

A further object is to provide an improved melody type of instrumenthaving a keyboard, an electrical tone frequency generating system, andoutput system, which is effective to sound the tones corresponding toany two keys Which-may be simultaneously depressed, or to sound thehighest and lowest of any three or more'keys which may be simultaneouslydepressed.

Other objects will appear from the following description, referencebeing had to the accompanying drawings in which:

Figure 1 is a wiring diagram of the keyboard anda portion of thefrequency generating system of the instrument;

Figure 1a is the wiring diagram of the circuits for frequency division,tone quality controlling, and for amplifying the signal and translatingit into sound; and

Figures 2, 3 and 4 are schematic wiring diagrams of modified forms ofdividing circuits.

The invention may be utilized for the production of tones in any desiredfrequency range, but has particular utility when used as the bass sec-'tion of an organ, and the invention is therefore described herein asembodiedin such form.

-Referring to Figure 1, the instrument is illustrated as comprising apedalboard of the usual range of 32 notes" extending from the low noteCB (32.703 C. P. S.) to the higher note G2 (196.00 C. P. S.). The keysbear reference characters corresponding to thelpitc'hes of the tonesordinarily produced upon depression thereof.

Each of the'keys C to G2 is provided with an actuator, indicated by adotted line in the drawmallyto be-in contact with a fixed contact l2,andare adapted when the associated key is depressed to break the contactwith the contact I2 and tomake contact with a fixed contact 14.Similarly, the switches II are normally in engagement with contacts I 3.and are adapted, when the key is depressed; to engage fixed contacts l5.It will be noted that the switch arms l0 are in series and that thecontact l2 for the key C0 is connectedto-ground, while the switch armIII for the highest key G2 is connected to a conductor [6. The contacts14 are connected to taps of an inductance'winding L2 wh-ich is ininductive relation with a feedback winding L4.

Inasimilarmanner the switches II are connected in series andnormallyengage their contacts 43. The contacts l5 of these switches areconnected to taps of a tuning inductance L3 which is in inductiverelation with a feedback winding L5;. The endsof theinductances L2 andba beyond thekey G2. are grounded. The switch I I for the key C0 isconnected to a conductor ll.

Theinductances L2 and L3 form parts of oscilla-torswhichincluderespectively triodes 20 and 2t; The. triode. 20 comprises. a cathode 22,a grid 24.;and a1plate26, while the triode 2| includes a cathode 23, a.grid 2 5.and a plateor anode 21. The conductor I6 is connected to thegrid 24 through a grid-bias resistor-R2, bypassed by condenser C2,; andis. connected to ground through a tuning condenser C4. Similarly,v theconductor I1 is connected'to the grid: 25 through a grid resistor R3',by-. passedby condenser C3, and is connected to ground through atuningcondenser C5.

Plate current is. supplied to the triode 2|! through a. load resistor R4connected-to the plate 26-.fromi.asuitable source of direct currentpotential-dndicated by a terminal +300 v. Similarly plate current forthe triode 2| is supplied 2 keysiwill; through the closure of its switch[0,

tunev theoscilltrtor'tube 20 to the pitch represented'by such key, whilethe lowermost of such depressed keys' will tune the oscillator tube 2|tothespitch-represented bysuch key. When three or more keys aresimultaneously depressed, depression of the intermediate keys has noeffect upon the tuning of the oscillators.

The output signal of the oscillator 20 is transmitted through a blockingcondenser C6 to a conductor 28, while the output signal of theoscillator 2| is transmitted through a blocking condenser C! to aconductor 29.

A non-linearly operating pentode 30 has its cathode 32 connected toground through a biasing resistor R6, and its grid 34 connected to theconductor 28 through a series grid resistor R8, the conductor 28 beingconnected to ground through a grid resistor RIO. The screen grid 36- ofthe pentode 30 is connected to a suitable source of direct currentpotential indicated as a terminal +125 v., while the suppressor grid 38is connected to the cathode 32. The plate 40 is connected to a suitablesource of plate potential indicated as a terminal +300 v, through a loadresistor BIZ, and is connected to a conductor 42 through a blocking andcharging condenser C8.

The oscillator 20 may have a distorted half wave rectifier type waveshape output, but the pentode 30 is biased so as to convert this waveinto a generally rectangularly shaped wave, since the negative portionof the input wave is cut off by virtue of the negative grid bias, whilethe positive portion of the input wave is cut off due to the change inthe input impedance of the grid circuit of the pentode. A pentode of the6J7G type operates satisfactorily for this purpose.

A pair of diodes 44, 46, which may be of the 61-16 type, are provided torectify the output of the pentode 30. For this purpose the cathode ofdiode 44 is connected to the conductor 42 while its plate is connectedto ground and the diode 44 will therefore conduct to ground the negativeportion of the output wave of the pentode 30. The diode 46, however, hasits plate connected to the conductor 42, while its cathode is connectedto a terminal 4'! which is connected to the plate 48 of a triode 50. Thecathode 52 of the triode 50 is connected to ground while its grid 54 isconnected through a current limiting resistor RM and a tertiary windingL6 with a suitable source of biasing potential indicated as a terminal 7V.

A charge accumulating and blocking condenser CIO has one terminalconnected to the terminal 4], while its other terminal is connected toground through a primary winding L8 of a transformer T2, the winding LBhaving a plate load resistor RIB connected in parallel therewith. Thecon-' denser C| has a value large with respect to that of the condenserC8, its value being determined by the number by which division of theoutput frequency of the pentode 30 is desired. As utilized in theembodiment of the invention disclosed, the condenser Clo will be chosento have such value that two positive pulses through the diode 46 will berequired to charge the condenser Cl 0 to a sufliciently high value thatplate current will flow in the triode 50 despite its substantialnegative bias. The triode 50 may be of the 6J5G type.

The transformer winding L8 is so phased with respect to the winding L6that as the plate current commences flowing through the triode 50, thebias on the grid 54 will be less (i. e., its potential will be raised toa less negative value than its normal 7 v. biasing potential), and as aresult, as soon as any plate current commences flowing through thetriode 50, the rate of flow will increase rapidly until the charge onthe condenser C|0 has been reduced to value such that further increasein the potential of the grid does not cause a corresponding increase inplate current. During the time that the plate current flow through thetriode 50 is decreasing, the inductance L6 will of course be effectiveto increase the grid bias at an accelerating rate so that the bias onthe triode 50 will rapidly return to a value beyond cut off. As aresult, the signal across the winding L8 will be a sharply peaked wave.

A secondary winding L|0 of the transformer T2 is connected to a secondnon-linear pentode 56 which operates in a manner identical with that ofthe pentode 30. The elements connected to the pentode 56 are likewisesubstantially identical with those associated with the pentode 32. Theoutput of the pentode 56 is connected through the blocking and chargingcondenser C|2 with a conductor 60, and the latter is connected to thecathode and plate respectively of diodes 62, 64, the plate of the tube62 being grounded and the cathode of tube 64 being connected to aterminal 66, The terminal 66 is connected to the plate of a triode 10which may be identical with the triode 50 and have similar circuitelements associated therewith. A blocking and charge accumulatingcondenser C|4 corresponds to the condenser C||| associated with thetriode 50. The output of the triode I0 is transmitted to a terminal 12through the secondary winding L|2 of a coupling and feedback transformerT4. One end of the secondary winding L|2 is grounded, While the otherend is connected to the terminal 12 through a decoupling resistor RIB.

As previously pointed out, the signal supplied by the oscillator 20 hasits frequency divided by 2 by virtue of the first frequency dividingstage which includes the pentode 30, diodes 44, 46 and triode 50. In asimilar way the pentode 56, diodes 62, 64 and triode l0 and theirassociated circuit elements constitute a second frequency dividingstage, dividing the frequency of the output of the first stage by 2, sothat the frequency of the signal across the secondary winding L|2 willbe one fourth of that of the oscillator 20.

Means are provided to successively divide the frequency of the output ofthe oscillator 2| by the factor of 2, the first stage of such frequencydivider system including a pentode 3|, diodes 45, 41, triode 5| andassociated circuit elements similar to those previously described. Thesecond stage of frequency division includes a pentode 51, diodes 63 and65 and triode 1|, the first stage being coupled to the second stagethrough a transformer T3 and the output of the second stage beingcoupled to the terminal 12 through a transformer T5, the second windingL|3 of which has one terminal connected to ground and th other terminalconnected to the terminal 12 through a decoupling resistor RIB.

Since these frequency division stages are essentially identical, theforegoing description of the stage which includes the non-linearlyamplifying pentode 3|! will suffice for an understanding of theconstruction and operation of the other stages, it being noted that theinput of the first stage which includes the non-linear amplifyingpentode 3| is connected to the conductor 29, thus to receive a signalfrom'the oscillator 2|.

The terminal 12 is connected to the grid of a linearly amplifyingpentode 82, the cathode and suppressor grid of which are connected toground, the screen grid 84 connected to a terminal v., and the plate 66connected through a load resistor R20 to a terminal +300 v. A- gridresistor R2I is connected between the grid 80 and a suitable terminalforsupplying the negative grid bias.

Connected 'intparallel with the load resistor R (1. e., between theplate 86 and a terminal +300 v., is a series of filtering meshes 88, 89,90

I04 connected to the ungrounded terminal of the secondary LIII through adecoupling resistor R24 as well as being connected through a decouplingresistor R with the ungrounded terminal of the secondary winding LII ofthe transformer T3. The grid I 84 is also connected to a suitableoperating bias potential through a grid resistor R21. The output of theamplifying pentode I02 is adapted to be modified by filtering meshesI08, I01, I08 and I09 upon selective opening of one or more controlswitches I I 0 in a manner similar to that described with the generallycorresponding output circuit of the pentode 82. The output of thepentode I02 is impressed upon the conductor 94 through a decouplingresistor R26.

A linearly amplifying pentode II2 has its grid II4 connected toconductors 28 and 29, decoupling resistors R28 and R29 respectively, andis supplied with a suitable operating bias through a grid resistor R3I,The output circuit of the pentode II2 includes a series offiltering-meshes H6, H1, H8 and II9 adapted to be selectively renderedeffective by opening one or more of a plurality of switches I22. Theoutput of the pentode H2 is also coupled to the conductor 94 through adecoupling resistor R30. The pentodes I I 2 and I 02, and theirassociated circuit elements,

are essentially identical and for this reason these parts have not beendescribed in detail.

In using the instrument, it is played in the manner of a conventionalorgan pedal clavier with the exception, however, that the instrumentwill be capable of playing only two notes simultaneously; It is onlyupon extremely rare occasions in organ literature that the score' callsfor playing more than two pedal notes simultaneously, and even on suchrare occasions the organist seldom follows the score because of thedifficulty of execution. Thus, the pedal clavier instrument of thisinvention is, for all practical purposes, played in a manner exactly thesame as any polyphonic organ pedal clavier- As previously pointed out,the depression of any pedal results in connecting a predeterminedportion of the inductance L2 into the tuning circuit of the oscillator20, and in doing so, the switches I0 of all lower keys are disconnectedand thus rendered ineifective. Similarly, the depression of such keycauses the connection of a predetermined portion of the inductance L3 inthe tuning circuit for the oscillator 2|, and disconnects the switchesII of keys corresponding to higher pitches from the tuning circuit sothat thereafter depression has no effect upon the tuning oftheoscillator. Thus, the oscillator 20 will be tuned to the highest of anyof a plurality of simultaneously depressed pedals, while the oscillator2| will be tuned to the lowest of any of upon their grids.

such plurality of depressed keysl If only onekey is depressed;bothoscillators will be tuned to" the 2 same frequency. 7

It will be noted that the inductances L2 and L3 are variable forinitially tuning the oscillators, such variationbeing preferablyeffected by adjusting the air gaps in the cores of these coils. Thistuningmay be done initially in the course of production of theinstrument, and will ordinarily not require readjustment for longperiods of time.

Aspreviously pointed out, the signals from the oscillators 20:"and 2|,tuned to the desired fre' quencies by the depression of one or twopedals,

have their amplitude held constant by the am-- plitude limiting tubes 30and 3| respectively. Thus, the output waves of these tubes are ofuniform amplitude irrespective of variations in the frequency oramplitude of the signals impressed Because ofthis function of the tubes30 and 3I, the dividingsystem is rendered extremely stable.

Thus, the diodes 44, 46 and 45, 41 are supplied with signals of constantamplitude, and

relative to the capacity of the condenser 08 is so chosen that thepotential across the condenser CI!) will build up to a value sufficientto cause the plate current to flowthrough the triode50 when either 2, 3,4 or any reasonably large integral number of impulses have been suppliedto the-condenser CIO. Although the operation of the circuits associatedwith the tubes 30 and 50 has been described as producing a frequencydivision by using 2 as the divisor, sub-multiples of the input frequencyusing other integers of 3 and higher as divisors may be employed. Thisdivider circuit may be used to divide the frequency by divisors runningupinto the thousands, and its division will be mathematicallyexact,depending upon the stability of the circuit elements. Using circuitelements of mathematically accurate divisions by a factor of 10 mayeasily be obtained, and division by higher divisors may be obtainedwithin relatively small percentage variations from mathematically exactfrequency division.

Assuming, as initially described, that division of the stage includingthe tubes 30, 50 and 3 I, 5|

is by a factor of 2, the output of these stages will a be an octavelower than the input frequency, and

organ nomenclature, the switches 92 correspond A to the I6 stops of thepedal division, while the switches IIO correspond to the 8' stops 'ofthe pedal division and the switches I22 correspond to the 4' stops ofthe pedal division. By operating the switches of these several groups invarious combinations, complex pedal tones consisting of octavely relatedtone qualities may be produced.

While the invention has been described as applied to the production ofthe tones controlled by a pedalboard, it will be clear to those skilledin the art that by suitable changes in the circuit elements theregisterof the instrument-maybe commercial tolerances, I

changed. For example, one of the oscillators 20, 2| together with aseries of cascaded stages of frequency division might be utilized as thefrequency generating apparatus for instruments of the types shown inHammond et al. Patent No. 2,233,258 or in my prior Patent No. 2,254,284.

The dividing circuit of the invention is particularly adapted fordivision of frequency of a variable frequency oscillator or othervariable frequency source because it is extremely stable throughout awide range of the input frequency. Thus, substantial changes in theinput frequency do not in any way impair the stability of the dividingstages. The reason for this is that each change that occurs in eithervoltage or current in the circuit elements which are connected togetherto form the divider system is initiated solely by the presence of asignal pulse transmitted by condenser C8 to a divider system. Forexample, the charge on condenser CIO increases by discreet increments,each increment of voltage being a reflection of a change in inputconditions on the grid 34 of tube 30, which is supplied by the signalsource. Thus, the amplitude at which the tube 50 discharges is afunction of the number of times that condenser C8 has charged condenserCIO and is not a function of the absolute frequency generated by theoscillators 20 or 2|.

In this respect this frequency divider differs in operation fromrelaxing dividers, from multivibrators, blocking oscillators, etc. Inthese latter types of frequency controlled devices there are change inpolarity, voltage, and current in the elements of the oscillator systemwhich change, not because of the presence of a controlling signal, butbecause of their own time constant functions, e. g., the charging of arelaxation condenser through a charging resistance after said condenserhas been discharged by a gaseous discharge tube having a grid which wasoperated positively by a controlling input signal. In the latterexemplary case the controlling signal operates to cause the discharge ofthe condenser, but the rate of charging of the condenser is determinedby constants of the circuit elements associated with the condenser, andthe rate is such that frequency division by some factor would occur fora given input frequency. Thus, this type of frequency divider dividescertain frequencies only, whereas the frequency divided of thisinvention divides all frequencies over an extremely wide audio frequencyspectrum. There are no time constant elements in the frequency dividerwhich are in any Way comparable in time to the period of the frequencybeing divided. All potential changes in the operation of the dividercircuit of this invention are signal controlled.

This non-linear, non-time constant frequency dividing principle of theinvention may be embodied in other forms such as illustrated in Figs. 2,3, and 4.

In the circuit of Fig. 2, a source I30 of variable frequency suppliesimpulses through a. condenser C8, conductor 42 and rectifier diodes 44and 46 to a condenser CIO, in the same manner as previously describedwith reference to Fig. 1a.. In this circuit, however, the charge on thecondenser CIO affects the voltage at the plate I32 of a Thyratron typeof gaseous discharge tube I34, which may be, for example, of the 885type. The condenser CI is coupled to the plate I32 through a smallinductance LIB and protective resistor R36. The grid I35 of tube I34 isconnected to a biasing voltage source, indicated as a terminal -9 v.,through a protective resistor R31, but the grid is not utilized forcontrol purposes, the 885 type tube being utilized merely as a gasdischarge diode tube. A cold cathode gas diode might be substituted forthe Thyratron I34, but the latter is preferred because of its highdegree of stability. In the case of the Thyratron I34, the heatedcathode I30 thereof is connected to ground, and the positive signal fromthe rectifier diode 46 is impressed upon the plate I32. If, however, acold cathode diode is used in place of the Thyratron I34, either thepositive or negative pulse from the rectifier tubes 44, 46 may beimpressed upon one plate of the diode.

As soon the condenser CIO has accumulated a sufficient potential tocause ignition of the Thyratron I34, the latter will discharge thecondenser CIO substantially to ground potential. The signal thusproduced in the primary I40 of an output transformer T6 may be utilizedto provide a signal one half that of the source I30 to a conductor I42,and may also be utilized as an input for an amplitude limiting pentode5B of a second frequency dividing stage.

In principle, the operation of the circuit of Fig. 2 is the same as thatshown in Fig. 1a, since the condenser CIO is incrementally chargedthrough the condenser C8 to a value such that it causes an amplituderesponsive discharge apparatus, in the form of the Thyratron I34, tofunction. It will be noted that in the circuit of Fig. 2, just as inFig. 1a, there are not circuit elements associated with the ThyratronI34, which provide a time constant comparable to the period of thesignal. Thus, this gaseous discharge frequency divider is unlike theusual gaseous discharge relaxing oscillator type frequency divider inthat all circuit functions are initiated solely by the signal, and thusthe controlling frequency plays no part in the frequency division ratio.

In Fig. 3, the circuit includes the variable frequency source I30 andrectifying circuits similar to those of Figs 1a and 2. The positivepulses of the rectified input signal are thus accumulated on thecondenser CIO, one terminal of which is connected to the plate I42 of atriode I44, such for example, as the 6J5G type. The grid I46 of thetriode I44 is connected through a series grid resistor R40 and a gridresistor RM to a source of biasing potential indicated as a terminalI41. The cathode I48 of the triode I44 is connected to ground. Theoutput of the triode I44 is coupled through a condenser CI2 to the gridI50 of a triode I52, the grid I50 being connected to a suitable biasingpotential source through a grid resistor R42. The plate I54 of thetriode I52 is connected to a suitable source of plate voltage indicatedas a terminal +300 v. through a load resistor R44. The plate I54 is alsoconnected through a feedback condenser CI4 to a terminal I49intermediate the resistors R40 and RM, The output of the triode I52 iscoupled through a blocking condenser CIE to the input of a currentlimiting pentode 56 corresponding to the tube 56 in the previouslydescribed circuits.

The circuit of Fig. 3 operates to divide the frequency of the source I30in the following manner: As the condenser CIO attains a chargesulficient to cause the triode I 44 to start to conduct plate current,such conduction is rapidly increased to effect a substantial dischargeof condenser CIO by virtue of the fact that tube I 52 serves as a phaseinverter to provide a signal of positive polarity through feedbackcondenser C'It-to the g'rid I 46, th-us increasing the plate current-ortube l ll until condenser CIO is discharged and further-increaseinpositiveness of the'grid I46 has no effect. "In practice, this'dis-"charge takesplace in an extremely short spaceof time compared to thefrequency of the source I30. Thus, thecircuit of Fig. 3 corresponds to ithat of Fig-dd, it being noted, however, that the I phase inversion inthe grid circuit is accomplished through the triode' I52 in "the circuitofFig. 3,

Whereas in the circuit of Fig. 1, this phaseinversion is accomplishedthrough the use of the tertiary winding L3-of the transformer T2.

A further modified form "of frequency dividing circuit which doesnothave any frequency reso nantor timing constants associated therewith,but which instead has its operation controlled solely by the applicationof impulse of the frequency to be divided, is shown in Fig. 4., In this--.figure a pair of Thyratrons I60, IGI, have their" grids-I62, I63connected to the'sour'ce I30 through blocking and decoupling condensersCI8 and CIS respectively. The grids'I62; I03 arecon'nected to a'suitablesource of biasing potential indicated as a terminal -17 v. through gridresistors R50 and RSI respectively. Protective resistors R52 and R53 maybe provided for the grids I62 and The plates I66 and IE1 of theThyratrons I60 and IIlI are respectively connected to a suitable platecurrentpot'ential source indicated as terminals +170 v. through loadresistors R54 and R55, as wellasthroughlow va'lue protective resistorsR56 and R51 respectively. The plates I60 and I! are coupled through arelatively large condenser C20. The cathodeI68 of the ThyratronISO-maybe connected to ground, while the cathodeIGS of the Thyratron I6Imay be connectedito ground through a' resistor R60 across which anoutput signalmmay be derivedthr'ough a blocking condenser C2I,-- suchsignal being impressed upon the grid of. a limiting pentode 56,

operating as previously described.

In the operation of the dividing circuit of Fig. 4, 'signal' pulse fromthe source I30 is simultaneously-impressed upon-the grids I62 and I03.However, due to unavoidable difierence's' inthe parameters of thesetubes and thecircuit elements associ'atedtherewith, only one ofthese'tubes is 'renderedconductive, and the other tube is' im-Inedi'ately prevented from reaching a discharge c'ondition'because ofthe following factors. Assume that upon impressing a positive pulse fromthe source I30 upon the grids of these tubes, the gas of the tube I00ionizes. The resultant plate current flow in this tube lowers thepotential at the junction H0, and hence upon the junction I II,sufficiently to lower the potential on the plate Nil below the ignitionpoint for a period of time in excess of the deionization time, but stillsmall by comparison with the period of the frequency being divided.Thus, if the tube IEI was ionized at the time that the positive impulsewas impressed upon its grid, it will be deionized.

Such conditions will continue until the next positive pulse from thesource I30 finds the grid I02 in an already ionized gaseous dischargepath between the cathode I68 and plate I50, and thus has no control.However, the pulse impressed upon the grid I63 is effective to causeionization to occur in. the tube IBI and thus lowers the potential atthe point Ill, and correspondingly the potential at the point I10, tothe deionization point of the tube I60. This cycle is repeated with eachalternate positive pulse from the source "'shape, 'will have a frequencyone halfthat of the source I30.

, It will be noted that this output or quotient rrequenc is notdependent upon any time constants of the elements associated with thesetubes I60, IGI; and thatthe alternate discharge of the tubes I00 and I6| is controlled solely by the application of the controlling signalfrom the source I30. Thus, this apparatus is effective to divide thefrequency of the source I30 over a very substantial range of the audiofrequency spectrum, such as 4 or 5octaves.

The divider circuit of Fig. 4 differs fromthose of Figs. 1a, 2 and 3' inthat it iscapable of division -only by thefactor of 2, whereas thecircuits of Figsvla, 2 and-3 are capable of dividing by any integraldivisor factor. ''However, all of the divider circuits-disclosedhereinhave the distinguishing feature that all of their voltage,current,

-- and polarity changes'resp'ond-only upon the application' ofacontrollingSignalQwhich is not the case, for instance, ofcontrolledrelaxation devices or the like.

While I have sho'wn and described a particular embodiment of 'myinvention it will be apparent to those skilled-in the art that numerousmodifications and variations maybe made in the form and constructionthereof, without departing from the more fundamental principles of'theinvention.- I therefore desire, by-the followingclaims, to includewithin the scope'of my invention all I such similara'nd modifiedforms ofthe apparatus disclosedyby which substantially the results ofthe'invention may be obtained by substantially the same or equivalentmeans. I claim:

T 1. In an*electrical--musical instrument having an output systemincluding electroacoustic translating means, the combinationof anelectrical pulse signal generator of dividend frequency, a plurality ofplaying keys, means operable by said keys for selectively tuning saidgenerator to an audio frequency related to the nominal pitchcorresponding to :the operated key, a frequency dividingcircuit-containing a negative reactance frequency divider element, anon-linear electron discharge device coupled to said negative reactanceelement.-a coupling between said pulse generator and'said' electrondischarge device such that all potential changes and polarity reversalson said frequency dividing negative reactive element are initiatedsolely by the application of said signal, said frequency dividingcircuit thereby producing a quotient frequency related to said dividendfrequency by an integral divisor, said divisor remaining a constant overa wide audio frequency spectrum exceeding one octave of dividend inputfrequency, signal collecting means for said pulse signal generator,signal collecting means for said frequency dividing means, andselectively operable means coupling either or both of said signalcollecting means to the output system of the instrument.

2. In an electrical musical instrument having an output system includingelectroacoustic translating means, an adjustable frequency oscillator,key actuated means for determining the frequency at which saidoscillator operates, means coupled to the oscillator and controlledsolely by the number of electrical impulses produced by said oscillatorto produce a rectangular wave impulse for every second impulse providedby said oscillator, and a tone quality controlling transmission circuitcoupling said means to the output system of the instrument.

3. In an electrical musical instrument having an output system includingelectroacoustic translating means, the combination of a source ofelectrical impulses of variable frequency, playing keys operable todetermine the frequency of the impulses derived from said source, meansto convert said impulses into electrical pulses of uniform amplitude,means to accumulate said pulses, electrical discharge means responsiveto the accumulation of a predetermined number of said pulses by saidlast named means to cause the discharge thereof, and means coupling saiddischarge means to said output system.

4. In an electrical musical instrument having an output system includingelectroacoustic translating means, a variable frequency source ofelectrical impulses of uniform amplitude, a plurality of playing keys,means operable by said keys to vary the frequency of said source, meansfor accumulating the electrical charges of said impulses, a deviceresponsive solely to the total charge on said accumulating means tocause rapid discharge thereof, and means for coupling said device to theoutput system of the instrument.

5. In an electrical musical instrument having an output system includingelectroacoustic translating means and having a pedalboard comprising aplurality of keys, the combination of a pair of oscillators, circuitscompleted upon depression of two or more of said keys to tune one ofsaid oscillators to a frequency related to the pitch corresponding tothe lowest of the depressed keys and to tune the other of saidoscillators to a frequency related to the pitch corresponding to thehighest of the depressed keys, separate means for dividing thefrequencies of the signals produced by said oscillators to producesub-multiple frequency signals, and tone control circuits for couplingsaid last named means to the output system.

6. In an electrical musical instrument, means for dividing the frequencyof a source of constant amplitude electrical impulses comprising, arectifier, reactive means coupling said rectifier to the source ofimpulses, a charge storing condenser coupled to said rectifier toreceive the output thereof, and relaxation means efiective to dischargesaid condenser whenever the potential across said condenser exceeds apredetermined value.

7. In an electrical musical instrument having an amplifying andelectroacoustic translating system, the combination of a tunablevariable frequency signal generating oscillator, a plurality of playingkeys, means operated by said keys to vary the tuning of said oscillatorand to cause it to oscillate at a frequency related to an operated key,a pair of similar electron discharge devices, each comprising an inputand a plate circuit, and cathode, grid and plate electrodes, meansintercoupling the plates and grids of said devices, means for couplingthe output of said oscillator to the input circuits of both oi. saiddevices, said couplings between the plates and grids of said devicesbeing arranged to cause voltages on said electrodes of value tomaterially reduce plate current flow in one of said devices upon anincrease in the flow of plate current in the other of said devices andvice versa, whereby said devices will alternately be rendered ofincreased conductivity upon receiving successive signal impulses fromsaid oscillator and produce a wave in the plate circuits of each of saiddevices comprising substantially solely a fundamental of one-half thefrequency of said oscillator and a musically desirable series of oddharmonics of said fundamental frequency, and means for selectivelycoupling one of said devices or said oscillator, or both, to theamplifying and electroacoustic translating system.

JOHN M. HANERT.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,203,432 George June 4, 19402,254,284 Hanert Sept. 2, 1941 2,276,390 Hanert Mar. 17, 1942 2,039,119Schlesinger Apr. 28, 1936 2,047,533 Von Ardenne July 14, 1936 2,284,101Robins May 26, 1942 2,185,635 Kock et a1. Jan. 2, 1940 2,158,285 KochMay 16, 1939 2,305,625 Lauer Dec. 22, 1942 2,331,986 Lauer Oct. 19, 19432,349,810 Cook May 30, 1944 2,310,105 Michel Feb. 2, 1943 2,113,011White Apr. 5, 1938

